Single venipuncture needles have been used to cyclically remove untreated blood from a patient and return treated blood to a patient, e.g., in conjunction with fluid flow transfer devices such as dialyzers connected to the needles via arterial and venous flow lines and drip chambers.
One or two pumps can be used, and the pumps and valves on the flow lines are controlled so as to provide flow of untreated blood from the patient and into the arterial line during an arterial phase and flow of treated blood through the venous line to the patient during a venous phase, e.g. as is described in Brose U.S. Pat. No. 4,643,14. If two pumps are used, they are generally alternately operated so that only one is on at one time. If one pump is used, it is operated continuously, and the pressures vary widely during the arterial and venous phases.